Foldable top materials are well known for folding tops of convertible vehicles. Such top materials are connected to the vehicle by means of a suitable articulated folding frame in order that the folding top may be moved between its open position and its closed position. The top material of state of the art vehicles is generally constructed in the form of a composite material which consists of two or more layers.
DE 199 49 878 A1 and DE 199 49 888 A1 each describe a convertible top material which comprises an outer top material and a casting resin layer which is attached to the outer top material on the vehicle interior side. According to DE 199 49 878 A1, top element side connecting elements are secured in the casting resin layer in order that connection to a top frame may be ensured. In the case of DE 199 49 888 A1, the casting resin layer serves as insulation, and also as stabilization against inflation. Here a thermally and acoustically insulating insulation layer, formed from a foamable plastic, is additionally provided between the casting resin layer and the outer top material.
DE 10 2005 006 033 A1 shows a top material in the form of a composite material for a foldable vehicle roof. This composite material comprises an underlayer, which faces the vehicle interior and is constructed, at least regionally, as a woven textile layer, a midlayer, and an outer leather layer, which are attached to the underlayer, in each case on a side remote from the vehicle interior. The outer leather layer is said to combine with the underlying layers to endow the top material with a longer life.
One of the intended functions of an insulation layer, usually made of a foamed plastic, in prior art top materials is that of providing acoustical insulation. However, such an insulation layer in the form of a foamed plastic is not ideal for acoustical insulation over a wide frequency range.